require

require(...) loads the specified JavaScript, JSON, or JSON5 file, allowing to split your configuration across multiple files.

A better name for this function might be "include".

If the supplied path string ends with .js, the file is interpreted as JavaScript code, almost as though its contents had been included in the currently-executing file. If the path string ends with .json or .json5 (case insensitive), require() returns the JSON.parse() of the file's contents.

If the path string begins with a ./, it is interpreted relative to the currently-loading file (which may not be the file where the require() statement is, if called within a function). Otherwise it is interpreted relative to the program's working directory at the time of the call.

Example 1: Simple

In this example, we separate our macros in one file, and put groups of domains in 3 other files. The result is a cleaner separation of code vs. domains.

dnsconfig.js

require("lib/macros.json");

require("domains/main.json");
require("domains/parked.json");
require("domains/otherstuff.json");

Example 2: Complex

Here's a more complex example:

dnsconfig.js

require("kubernetes/clusters.js");

D("example.com", REG_MY_PROVIDER, DnsProvider(DSP_MY_PROVIDER),
    IncludeKubernetes(),
END);

kubernetes/clusters.js

require("./clusters/prod.js");
require("./clusters/dev.js");

function IncludeKubernetes() {
    return [includeK8Sprod(), includeK8Sdev()];
}

kubernetes/clusters/prod.js

function includeK8Sprod() {
    return [
        // ...
    ];
}

kubernetes/clusters/dev.js

function includeK8Sdev() {
    return [
        // ...
    ];
}

Example 3: JSON and JSON5

Requiring JSON files initializes variables:

dnsconfig.js

var domains = require("./domain-ip-map.json")

var REG_MY_PROVIDER = NewRegistrar("none");
var DSP_MY_DNSSERVER = NewDnsProvider("none");

for (var domain in domains) {
    D(domain, REG_MY_PROVIDER, DSP_MY_DNSSERVER,
        A("@", domains[domain])
    );
}

domain-ip-map.json

{
    "example.com": "1.1.1.1",
    "other-example.com``": "5.5.5.5"
}

JSON5 works the same way, but the filename ends in .json5. (Note: JSON5 features are supported whether the filename ends with .json or .json5. However please don't rely on JSON5 features in a .json file as this may change some day.)

Notes

require() is much closer to PHP's include() function than it is to node's require().

Node's require() only includes a file once. In contrast, DNSControl's require() is actually an imperative command to load the file and execute the code or parse the data from it. For example if two files both require("./tools.js"), then it will be loaded twice, whereas in node.js it would only be loaded once.